CRUSTACEANS. 501 



attain a size of nine or ten inches in length, three of them being 

 considered quite sufficient for a meal. 



The London market is chiefly supplied with prawns from the Isle 

 of Wight and Hampshire coast. 



Like the prawn, the shrimp has many varieties. The common 

 shrimp (Crangon vulgar is) is about two and a half inches long, 

 from the eye to the extremity of the tail. It is also furnished with 

 a rounded articulated carapace, with two antennae. The eyes are 

 prominent, marked, and near each other ; the tail flat, laminated, and 

 hirsute. The shrimp is not very unlike the prawn in general appear- 

 ance, but is of a much less complex and finished structure. 



In colour it is greyish brown, clotted all over with dark brown. 

 In this species heat does not improve the colour. 



This variety is one of the most abundant of all coast Crustacea, 

 swimming about and laying on the sands (which they closely resemble 

 in colour) in immense shoals. Sometimes they are also found in deep 

 water, but the margin of the sea is their favourite habitat. It may 

 be added, that large quantities of the smaller palaemonidab are caught 

 with and sold as shrimps. Shrimps are in spawn all the year 

 through, and cast their shells during the three months of spring. 



The Entomostraea of Milne Edwards, or the Lophyropoda of 

 Latreille, have no suctorial mouth or mandibles capable of mastication ; 

 their maxillae are lamellose, and they have never more than ten 

 swimming feet, and have from one to two eyes on stalks, and live in 

 fresh water. There are two principal genera; the Copepoda of 

 Edwards, and the Ostracoda. As a type of the first, we may mention 

 Cyclops vulgaris (Leach), which, true to its name, has but one eye. 

 But the genus Pontia of the same family has two. As a type of the 

 second order, Ostracoda, we will specify the numerous family of the 

 Cyprides, whose animals are enclosed in a bivalve shell, which causes 

 their remains in Secondary strata to be classed with bivalve molluscs. 



